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- Author or Editor: John Masiunas x
In 2004 and 2005, potted white oak seedlings 0.6 m in height were treated with six herbicide treatments at three concentrations, 1/4, 1/10, and 1/100× of the standard field use rate. These herbicides and their standard field use rate of active ingredient (a.i.) included 2,4-D at 1.5 kg/ha, 2,4-D + glyphosate at 0.8 kg/ha + 1 kg/ha, acetochlor + atrazine at 3.5 kg/ha, dicamba at 0.7 kg/ha, glyphosate at 1.1 kg/ha and metolachlor at 2.0 kg/ha. The seedlings were treated at three growth stages: swollen buds, leaves unfolding, and expanded leaves. A compressed air spraying chamber delivering 187 L/ha was used to apply the herbicides. After treatment, the containers were placed in an open field plot in a completely randomized design. Oak seedlings were most susceptible to herbicide injury at all concentrations, at the leaves unfolding stage. Symptoms on seedlings treated with 2,4-D and dicamba at the leaves unfolding stage included leaf cupping and rolling, leaf curling, leaf rolling downward from leaf margin, and unusual elongation at leaf tip. Glyphosate + 2,4-D applications resulted in leaf cupping, yellowing, leaf rolling downward from leaf margin and abnormal leaf tips. Glyphosate symptoms ranged from leaf yellowing and browning, to slight browning of interveinal leaf tissues. Acetochlor + atrazine, or metolachlor alone caused the abnormality referred to as “leaf tatters” where in severe cases, only the main veins are present with limited amounts of interveinal tissues. Detailed description of the injury symptoms, supplemented with photographs are posted on a web site: http://www.nres.uiuc.edu/research/herbicide_research/index.htm
In some years, the emerging leaves of white oak and, to a lesser extent, of red oak in the Midwest have developed abnormally. This abnormality is referred to as leaf tatters. Reports to state foresters and Extension specialists associated tatters with herbicide applications. In 2005, white and red oak seedlings were treated in a spray chamber delivering 187 L/ha, with seven herbicides at three concentrations, 1/4×, 1/10×, and 1/100× of the standard field use rate. These herbicides and their standard field use rate of the active ingredients included atrazine at 2.3 kg/ha and chloroacetanilide herbicides: acetochlor at 2.0 kg/ha, metolachlor at 2.1 kg/ha, and dimethenamid at 0.8 kg/ha alone or mixed with atrazine at 2.3 kg/ha, at the leaves unfolding stage. After treatment, oaks were placed outdoors in a randomized complete-block design. Leaf symptoms in our study were similar to those seen in the landscape. In chloroacetanilide-treated white and red oak seedlings, browning of interveinal leaf tissues was noticed 5–6 days after treatment. The dried leaf tissues then dropped off, leaving only the main vein with little interveinal leaf area. In few seedlings treated with atrazine, the leaf tissues turned yellow to brown, while in few others, interveinal tissue damage was restricted, leaving small holes in the leaf. When chloroacetanilide herbicides were applied with atrazine, the dominant symptoms were those of leaf tatters. A few seedlings treated with dimethenamid and atrazine had predominately atrazine symptoms. Although new growth later in the season was not injured, the leaves with tatters remained on the plant until the end of the growing season. The study will be repeated in 2006.
Previous research by the authors found simulated acetochlor (with atrazine) and s-metolachlor drift to white oak at the leaf unfolding stage caused loss of interveinal tissues (leaf tatters). Reports of leaf tatters in the landscape and nursery settings are more common on white oak (Quercus alba L.) than on northern red oak (Quercus rubra L.). Our objectives were to determine if white and northern red oak differed in susceptibility to chloroacetanilide herbicides, if injury varied between chloroacetanilide herbicides, and if adding atrazine increased leaf injury. Two-year-old seedlings at the leaf unfolding stage were treated with acetochlor, s-metolachlor, and dimethenamid-P alone or combined with atrazine at 1%, 10%, and 25% of the standard field use rate. Within 6 days, all chloroacetanilides at 10% and 25% field use rates, alone or combined with atrazine, caused leaf tatter injury in both species. Acetochlor, s-metolachlor, and dimethenamid-P caused a similar type of leaf injury. Atrazine did not cause loss of leaf tissues or increase injury from chloroacetanilides. At 1% field use rate, only acetochlor, acetochlor + atrazine, and dimethenamid-P caused leaf injury to northern red oaks. The white oaks were not injured by all of the chloroacetanilide treatments at 1% field use rate. The northern red oaks were slightly more susceptible to chloroacetanilides compared with the white oaks. A second study found acetochlor only injured northern red oak when applied at the leaf unfolding stage and only at 25% of field use rate. Acetochlor at 1% field use rate did not injure red oak. Research is needed to explain the greater frequency of leaf tatters on white oaks than on northern red oaks in the landscape and to develop strategies to avoid tree injury.
Field experiments were conducted in 1992 and 1993 to determine the effect of N fertility, cropping system, redroot pigweed (Amaranthus retroflexus L.) density, and harvesting frequency on collard (Brassica oleracea var. acephala D.C) and cowpea [Vigna unguiculata (L.) Walp.] growth. The N fertilization regimes were 0, 80, 160, and 240 kg·ha-1, applied as urea in a split application. Four weeks after crop planting, redroot pigweed was seeded at 0, 300, and 1200 seeds/m2. Between weeks 6 and 12, collard leaves were harvested at 1- to 3-week intervals. Year, N fertility, and cropping system interacted to determine collard leaf number and mass. For example, in 1992, with N at 160 kg·ha-1, collards intercropped had more total leaf mass than those monocropped. Pigweed density had no effect on collard yields, which were greatest from the 3-week harvest frequency. Cropping system and pigweed density interacted to determine cowpea vine length, shoot dry mass, and branching. The high density of pigweed caused a 56% reduction of cowpea dry mass in 1992.
Herbicide drift to landscape and woodland trees is a particular concern in midwestern United States where the topography is relatively flat, large-scale agriculture relies on herbicides, and housing developments and woodlands are intermingled with agricultural fields. Recently, leaf abnormalities (called leaf tatters) have been reported on white oak (Quercus alba L.). We evaluated the effects of field corn herbicides on white oak at the swollen bud, leaf unfolding, and expanded leaf stages. Container-grown white oak seedlings were treated with 1%, 10%, and 25% standard field use rates of 2,4-D isooctyl ester, glyphosate, 2,4-D isooctyl ester + glyphosate, dicamba, acetochlor + atrazine, and metolachlor. Loss of interveinal tissues (leaf tatters) occurred after treatment with the chloroacetanilide herbicides, acetochlor (+ atrazine) and metolachlor, only when oaks were in the leaf unfolding stage. No other herbicide caused tatter-like symptoms. Dicamba and 2,4-D ester applied at the leaf unfolding stage caused leaf cupping, downward rolling of leaf margins, elongation of leaf tips, leaf strapping with parallel veination, and initial leaf cupping followed by death of the growing point. Glyphosate applied at either the leaf unfolding or expanded leaf stage caused leaf chlorosis and necrosis, leaf tip browning, and curling of leaves. Herbicide applications near white oak should be timed before leaf unfolding or after the expanded leaf stages.
Eastern black nightshade (Solanum ptycanthum) and black (Solanum nigrum) nightshade are difficult to control in tomato, interfering with harvest and decreasing fruit quality and yield. In irrigated tomatoes, soil water depletion was greater as nightshade density increased. However, tomato yield loss due to black nightshade was greatest at the lower weed densities. As density increases, photosynthetic activity (photosynthetic rates, stomatal conductance, intercellular CO2 concentration, and stomatal resistance) of black nightshade is more affected than eastern black nightshade. Photosynthetic activity of tomato is the least affected. In greenhouse experiments where water was denied for approximately a week prior to measurement, tomatoes were more sensitive to water stress than were nightshades. Nightshades were more adapted to drought stress than were tomatoes.
Field and greenhouse experiments were conducted to determine the response of eastern black nightshade (Solanum ptycanthum), black nightshade (S. nigrum), and tomato (Lycopersicon esculentum Mill. cv. Heinz 6004) to water stress and the effect of nightshade-tomato competition on soil water content. In the greenhouse, plants were exposed to three water regimes induced by watering either daily, weekly, or biweekly. Water deficit caused a similar decrease in height, weight, and leaf area in all three species. There was more than a 50% reduction in height when the plants were watered biweekly compared with daily watering. Water stress caused a shift in biomass from shoots to roots in all three species. Black nightshade and tomato produced thinner leaves in response to water deficit. Companion field experiments were conducted during the 1989 and 1990 growing seasons in Urbana, Ill. Eastern black nightshade and black nightshade were transplanted at densities of 0.8, 1.6, 3.2, and 4.8 plants/m2, 5 days after tomatoes were transplanted. These nightshade densities caused significant reductions in soil water content. In 1989, only the highest density of either nightshade species reduced topsoil water content. In 1990, all densities of nightshade, except the two lowest densities of black nightshade, reduced topsoil water content. Eastern black nightshade consistently had a greater effect on tomato yield than black nightshade. Tomato yields averaged over both years were 17,000 and 8,000 kg·ha-1 at the highest (4.8 plants/m*) density of black and eastern black nightshade, respectively. The decrease in soil moisture from high densities of nightshade could not account for the reduced yields.
Path analysis is a statistical method for determining the magnitude and direction of multiple effects on a complex process. We used path analysis to assess 1) the impact of black nightshade(Solarium nigrum L.) or eastern black nightshade(Solarium ptycanthum Dun.) competition on the yield components of `Heinz 6004' processing tomato (Lycopersicon esculentum Mill.) and 2) the relationship between tomato yield components and total and marketable yield. Either black or eastern black nightshade was interplanted with tomatoes at population densities from 0 to 4.8/m2. Path analysis revealed that increasing weed population density led directly to fewer green and total fruit per plant, two components of marketable yield. However, the percentage of culls per plant and fruit weight were not affected by nightshade population density. Using correlation coefficients alone would have lead to the erroneous conclusion that the percentage of culls did not affect marketable yield; our path analysis demonstrated that decreasing the percentage of culls through breeding or cultural practices will strongly affect marketable yield. The total number of fruit was the most important yield component in determining total and marketable yields per plant. Breeding and management practices that maximize fruit set, increase maturity at harvest, and decrease the percentage of culls would be expected to increase marketable yield.
Field studies were conducted to determine insect and plant pathogen management effects on weed competitiveness and crop yield and to evaluate weed management impacts on insect pests, diseases, and crop yield. At similar densities, redroot pigweed (Amaranthus retroflexus L.) reduced snapbean (Phaseolus vulgaris L.) and cabbage (Brassica oleracea L. var capitata) yield more than that of common purslane (Portulaca oleracea L.), a low growing weed. In 1995, diamondback moth [Plutella xylostella (L.)] was greater on cabbage growing in plots with purslane than in plots of cabbage growing without weeds. Imported cabbageworm [Pieris rapae (L.)] was greater on cabbage growing in plots with either purslane or pigweed than when growing alone. However, the amount of feeding damage to cabbage was similar across treatments. Disease incidence was low, but fungicide treatments made redroot pigweed more competitive with snapbean, reducing yield in 1995.
A foam mulch system was developed that can be applied as an aqueous mixture of cotton and cellulose fibers, gums, starches, surfactants and saponins and dries to an one inch thick mat. This mulch may overcome the difficulty in applying and lack of persistence with natural mulches. Foam mulch also has the advantage of being able to be incorporated into the soil without requiring disposal like some plastic mulches. The objective of our study was to determine the effect of foam mulch and its color on weed control within the crop row and on yields of basil (Ocimum basilicum) and tomatoes (Lycopersicon esculentum). The foam mulch maintained its integrity for the entire growing season and provided weed control within the crop row comparable to black plastic mulch. The only weeds that emerged in the crop row were through holes in either the black or foam mulch. Foam mulch color did not affect weed control because regardless of color it did not allow light penetration andserved as a physical barrier impeding weed emergence. Basil shoot biomass was not affected by mulch treatment. Mulch color affected early, ripe fruit, and total yield of tomato. Tomato yields in the blue foam were greater than other treatments. Yields in the black foam mulch were similar to those in black plastic mulch. Further research is needed to characterize the effects of foam mulch on crop microenvironment. Currently foam mulch is being commercialized for use in the home landscape and other highvalue situations.